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    <title>ShellCheck: SC2017 – Increase precision by replacing `a/b*c` with `a*c/b`.</title>
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    <h1>SC2017 – ShellCheck Wiki</h1>
    <a href="https://github.com/koalaman/shellcheck/wiki/SC2017">See this page on GitHub</a>
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    <h2 id="increase-precision-by-replacing-abc-with-acb">Increase precision
by replacing <code>a/b*c</code> with <code>a*c/b</code>.</h2>
<h3 id="problematic-code">Problematic code:</h3>
<div class="sourceCode" id="cb1"><pre class="sourceCode sh"><code class="sourceCode bash"><span id="cb1-1"><a href="SC2017.html#cb1-1" aria-hidden="true" tabindex="-1"></a><span class="va">percent</span><span class="op">=</span><span class="va">$((count</span><span class="op">/</span><span class="va">total</span><span class="op">*</span><span class="dv">100</span><span class="va">))</span></span></code></pre></div>
<h3 id="correct-code">Correct code:</h3>
<div class="sourceCode" id="cb2"><pre class="sourceCode sh"><code class="sourceCode bash"><span id="cb2-1"><a href="SC2017.html#cb2-1" aria-hidden="true" tabindex="-1"></a><span class="va">percent</span><span class="op">=</span><span class="va">$((count</span><span class="op">*</span><span class="dv">100</span><span class="op">/</span><span class="va">total))</span></span></code></pre></div>
<h3 id="rationale">Rationale:</h3>
<p>If integer division is performed before multiplication, the
intermediate result will be truncated causing a loss of precision.</p>
<p>In this case, if <code>count=1</code> and <code>total=2</code>, then
the problematic code results in <code>percent=0</code>, while the
correct code gives <code>percent=50</code>.</p>
<h3 id="exceptions">Exceptions:</h3>
<p>If you want and expect truncation you can ignore this message.</p>
<p>ShellCheck doesn't warn when <code>b</code> and <code>c</code> are
identical expressions, e.g. <code>a/10*10</code>, under the assumption
that the intent is to rounded to the nearest 10 rather than the no-op of
multiply by <code>1</code>.</p>
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